Corrosion-resistant tube



Patented Nov. 24, 14 336 I 2,961,897 UNITED STATES PATENT OFFICE 2,061,897 CORROSION-RESISTANT TUBE Donald K. Crampton, Marion, and Newell W. Mitchell, Waterbury, onn., assignors to The Chase Companies, Incorporated, Waterbury, Conn., a corporation of Connecticut No Drawing. Application June 25, 1936, Serial No. 87,218

8 Claims. (Cl. 138-47) This invention relates to improvements in corno tin, and the balance copper. The inclusion rosion-resistant tubes, and more particularly, corof the 3% of tin not only raised the tensile rosion-resistant wrought-metal tubes formed of strength of the material in the worked and ancopper-base alloys containing copper, nickel, alunealed state from approximately 43,400 lbs. per minum and tin, with or without other ingredients square inch to 57,300 lbs. per square inch, but 5 which do not seriously impair the properties of did so without any loss of ductility; the elongathe alloy. tion in two inches being 34% for both of the al- This application is' a continuation-impart of loys just referred to. The foregoing clearly our application Serial No. 709,172, filed January shows that the inclusion of the tin added to the 31, 1934. tensile strength in an amount approximately 10 One object-of this invention is to provide atube 13,900 lbs. per square inch without, however, formed of a copper-base alloy having superior harmfully affecting the ductility. resistance to corrosion. Further studies showed that an alloy contain- Another object is to provide a tube formed of ing about 5% nickel, 3% aluminum, 3% tin and 5 a copper-base alloy having superior resistance to the balance copper, possessed a tensile strength corrosion and superior physical properties. a about 69,400 lbs. per square inch and an elonga- A further object is to provide a tube formed tion in twoinches of 42%, whereas an alloy of of a copper-base alloy having superior resistance about 5% nickel, 3% aluminum, no tin and the to corrosion with capacity for being readily hot balance substantially all copper, possessed a tenworked. sile strength of but 58,000 lbs. per square inch 20 A still further object is to providea tube formed and an elongation in two inches of 28%. Thus of a copper-base alloy having both superior reit appears that the inclusion of 3% tin in the sistance to corrosion and capacity for being conalloy just referred to increased the tensile veniently cold worked. strength some 11,400 lbs. per square inch, and

Another object is to provide a tube formed of at the same time accomplished what is unusual, 5 a corrosion-resistant copper-base alloy which may namely, an increase in elongation of some 14%. be conveniently worked, either hot or cold. Usually, changes in alloys which produce in- Other objects and advantages will appear to creased tensile strength will result in a correthose skilled in the art from the following, conspending decrease in elongation.

3o sidered in conjunction with the appended claims. Generally speaking, tests which have been con- In order that the pertinence of the following ducted indicate that an increased nickel con- I may be better understood, it may here be stated tent has relatively little efiect on the hot-workthat binary alloys of copper-nickel, copper-aluing properties of the alloy but serves to gradminum, and copper-tin are well known in the ually increase the hardness and toughness and, art, as are also ternary alloys of copper-nickelby the same token, increases the resistance to 35 aluminum, copper-nickel-timand copper-alumicold-working. With increasin aluminum o num-tin. v r tent, the hot workability seems to be appreciably The present invention contemplates wroughtimproved, but the cold-workability is, on the metal, corrosive-fluid-contact tubes, pipes and contrary, somewhat decreased. vIn general the the like, such for example, as condenser and higher the nickel and/or aluminum'content, a 40 heat-exchanger tubes formed of a copper-base relatively-lesser amount of tin is desirable in oralloy in which, in addition to a preponderant der to still preserve a commercially-workable amount of copper, nickel, aluminum and tin are product. From the standpoint of workabilityincluded in suitable'amounts, substantially withboth hot and cold-alloys containing from b t 5 in the limits-nickel about 4% to about 30%, 5% t b t 10% i k l, from ab t, 1% t .aluminum about 1/2% to about t about about 3% aluminum, and from about 1% to to about and copper oomprlsmg about 3% tin, have proved to be extremely satstontiouy o remainder that is, t or Without isfactory. Greater corrosion-resistance may be other ingredients which do not seriously impa1r obtainedhowever, by raising the tin content up the properties of the alloyflwhereby' Improved toward the 5% mark but with some loss in work- 50 ycorrosion-resistant characteristics are secured, ability. together wlth other advantages The properties above referred to were appar- Tensile strength, ductility, etc. ent when the material was in the annealed con-' A series of studies of alloys within the ranges dltion! but tests have also shown t the above set forth Show, for example, that an alloy vantages of the tin content were also apparent V composed f about 5% nickel, 1% aluminum, 3% when the material was in the age-hardened contin and a, balance substantially 3,11 copper, posditiOl'i. Most Of the alloys herein referred to sessed appreciably better physical properties than possess to a greater or lesser degree, capacity for one containing about 5% nickel, 1% aluminum, being age-hardened. o

C'o1rosionP-resistance A series of corrosion tests of the water-line type enduring for about one hundred days in dilute synthetic sea water at a temperature of 60 0. served to clearly demonstrate the possibility of securing superior all-around corrosionresistance by the inclusion of tin with nickel, aluminum and copper. The synthetic sea-water solution referred to has been previously found to be quite corrosive to copper-base alloys, as well as to other alloys, and represents, moreover, a condition which is very commonly encountered in commercial practice, such, for instance, as in harbors. The synthetic sea water employed in the tests now being referred to was of a concentration about one-sixth that of full strength sea water, and has been found from extensive tests to be in general more corrosive than normal sea water itself.

The results obtained from the corrosion tests above referred to are given below in terms of per cent loss of original tensile strength, and for purposes of comparison straight copper-nickelaluminum alloys are included, as well as socalled Admiralty brass, which latter alloy has heretofore been very largely used in condenser tubes, etc., subjected to corrosive waters:

Composition of alloy Cu Ni Al Sn Zn The foregoing table shows that all of the copper-nickel-aluminum alloys, as well as the copper-nickel-aluminum-tin alloys of the present invention, are markedly superior to the Admiralty brass (#5). What is most pertinent, however, the results tabulated clearly show the superior corrosion-resistance of the quaternary alloy of the present invention over that of the ternary copper-nickel-alurninum alloys. The corrosion-test results further show that I under the conditions referred to, the quaternary alloys of the present invention, with a 5% nickel content, are more resistant to corrosion with 3% aluminum than they are with but 1% aluminum.

Further corrosion tests in two other corrosive solutions confirm the corrosion-test results above given, as will be clear from the following table:

- Percent loss of Composition of alloy original tensile Per cent of loss of strength in 5% original tensile malic acid and strength in 1% sodium sulphuric acid g lorged solusolution; 1(0 day ion; ay exexposure water on N1 Al Sn posure (water line) 30 C line) 60 C.

No. 6 94 5 1 21 28 N0. 7-..- 93 5 l l 17 17 N0. 8--- 91 5 1 3 10 14 No. 92 5 3 17 29 N0. 10-- 91 5 3 1 16 14 N0. 89 5 3 3 l2 9 N0. 12-- 89 1O 1 23 No. 88 10 1 1 l3 18 The alloys referred to in the preceding table were all heat-treated for about one and onehalf hours at a temperature of 600 C. to build up a considerable surface-film with the intent of taking advantage as much as possible of the film-forming characteristic of the aluminum constituent.

The results of the foregoing tests in general confirm the findings from the previous corrosion tests hereinbefore tabulated, and indicate that the eifect of the larger aluminum content is not, however, here so marked as in the previous test referred to,but the beneficial effect of larger tin content is very marked.

The combined malic acid and sodium chloride solution referred to is comparable in its general eiTect to many corrosive food stuffs, and it has been found to have a very powerful corrosive effect on a wide variety of alloys. The 1% sulphuric acid solution referred to is representative of a relatively-strong acid-condition--a condition quite commonly found in practiceand very corrosive to a wide variety of alloys.

A further series of corrosion tests employing a markedly strong acid solution (5% H2804) is clearly indicative of the superior corrosion-re sistant properties of alloys of the present invention, as set forth in the following table. The alloys when subjected to the tests were in the annealed state.

Composition of Alloy Sn Mn Alloys Nos. 19, 20, 21 and 22 serve to show that the inclusion of manganese or zinc does not detract from the corrosion-resistance of the alloys under the conditions given. On the other hand, it may be stated that manganese serves as an excellent deoxidizer for such nickel-bearing alloys and the zinc serves to facilitate the making of sound castings.

As hereinbefore pointed out, the present invention contemplates a copper-nickel-aluminum-tin [alloy comprising essentially nickel about 4% to about 30%, aluminum about to about 4%, tin about to about 5%, and a balance substantially all copper, save that allowance should be made for miscellaneous ingredients present either as impurities or intentionally incorporated if desired.

The following represent a few specific alloys coming within the scope of the present invention in addition to those hereinbefore given and are to be considered in all respects as representative and not exhaustive:

Cu Ni Al Sn Si Fe Mn Zn P Cd The invention may be carried out in other specific ways than those herein set forth without acteristics of the invention,

, num; about /2% to about 5% and essential charand the present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. I

We claim:

1. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 4% to about 30% nickel; about to about 4% aluminum; about /2% to about 5% tin; and the balance substantially of copper.

2. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 4% to about 20% nickel; about /2% to about 4% alumitin; and the balance departing from the spirit substantially of copper.

3. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 4% to about 15% nickel; about /z% to about 4% aluminum; about /2% to about 5% tin; and the balance substantially of copper.

4. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 4% to about 10% nickel; about /2% to about 4% aluminum; about /z% to about 5% tin; and the balance substantially of copper.

5. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 5% to about 10% nickel; about 1% to about 3% aluminum; about 1% to about 3% tin; and the balance substantially of copper.

6. A corrosion-resistant wrought-metal tube formed from an alloy containing: about 20% nickel; about 2% aluminum; about 1% tin; and. the balance substantially of copper. I 7. A corrosion-resistant wrought-metal tube formed. from an alloy containing: about 10% nickel; about 3% aluminum; about 3% tin; and the balance substantially of copper.

8. A corrosion-resistant wrought-metal tube formed from an alloy containing; about 5% nickel; about 3% aluminum; about 3% the balance substantially of copper.

DONALD K. CRAMPTON. NEWELL W. MITCHELL.

tin; and 20 

